Process for treating a surface

ABSTRACT

A process for treating a surface ( 2 ) to clean or otherwise treat the surface ( 2 ) comprises a step of contacting the surface ( 2 ) with a particulate treating agent such that at least some of the particles ( 1 ) roll along at least a portion of the surface ( 2 ), wherein an angle of incidence of the particles ( 1 ) and the surface is between 0° and 60°. The particles ( 1 ) are dimensioned to effect a rolling movement along the surface ( 2 ). The treating agent is substantially non-aqueous. The particles ( 1 ) comprise a precipitate or agglomerate of an insoluble alkali metal carbonate. The process comprises a blasting operation or a manual application. The use of the process of the invention in dental applications such as teeth whitening and plaque removal, treating bone, and skin exfoliation, is also disclosed. Also disclosed is a treating agent which comprises a plurality of particles ( 1 ), the particles ( 1 ) being dimensioned to effect a rolling movement along a surface ( 2 ), wherein the treating agent is substantially non-aqueous.

TECHNICAL FIELD

The invention relates to a process for treating a surface to clean orotherwise treat the surface, the process being of the type which employsa treating agent comprising a plurality of particles.

BACKGROUND

Cleaning of the surfaces of various types of equipment and structures isoften desirable. Numerous processes and cleaning agents are known in theart. The choice of process and agent depends to a great extent on thecoating to be removed and on the substrate. In addition, the workingconditions and the environmental effects of the process and agent usedare becoming increasingly important factors when selecting an optimalcleaning technique.

Sand blasting and other abrasive techniques are quite applicable on hardsubstrates, but require special arrangements to meet the specificationrelated to environment and working conditions.

Less hard and durable substrates like aluminium, wood and compositematerials require processes and cleaning agents which do not causemechanical or chemical damage to the surface of the substrate.

International Patent Application No PCT/NO93/00137 in the name of NorskHydro A. S discloses a wet blasting process which employs an aqueousslurry of precipitated, non-soluble, calcium carbonate. The use of suchaqueous wet blasting agents has a number of disadvantages. The aqueousblasting slurries have a tendency to freeze when used in countries wheresevere winters are encountered. Further, the presence of water inblasting slurries can have the effect of contributing to erosion of thesurface being cleaned. This problem is particularly acute when thesurface being cleaned forms part of a structure or building. Moreover,the use of aqueous blasting slurries to treat surfaces having electricalcomponents can be particularly hazardous and can cause corrosion.

It is an object of the invention to overcome at least some of the abovedisadvantages.

STATEMENTS OF INVENTION

According to the invention, there is provided a process for treating asurface to clean or otherwise treat the surface, the process being ofthe type which employs a treating agent comprising a plurality ofparticles, the process comprising the step of contacting the surfacewith the treating agent such that at least some of the particles rollalong at least a portion of the surface, wherein an angle of incidenceof the particles and the surface is between 0° and 60°, wherein theparticles are dimensioned to effect a rolling movement along thesurface, and wherein the treating agent is preferably substantiallynon-aqueous.

In this specification, the term “substantially non-aqueous” as appliedto treating agents should be understood as meaning treating agentshaving less than 5% water. A minimal amount of water is often includedin the treating agent to minimise the production of dust.

In one embodiment of the invention, the treating agent comprises lessthan 5% water, suitably less than 4% water, typically less than 3%water, preferably less than 2% water, and ideally less than 1% water.

When the projected particle impacts the substrate at a low angle ofincidence it rolls along the surface, rubbing and absorbing the coatingfrom the surface.

In one embodiment of the invention, the treating agent includes annon-aqueous solvent such as, for example, an alcohol.

In a preferred embodiment of the invention, the particles arenon-crystalline.

In one preferred embodiment of the invention, the particles comprise aprecipitate or agglomerate of an insoluble alkali metal salt. Typically,the salt is a carbonate. Suitably the metal is calcium or magnesium.

Preferably, the particles are generally round. In this specification theterm “generally round” as applied to particles should be understood tomean any shape which of particle which enables the particle to easilyassume a rolling motion when moved along a surface. As such, while theterm is primarily intended to refer to spherical particles, it is notintended to exclude other types of spheroids such as spheres having anoblong or elliptical shape. Typically, the particles will have anirregular surface configuration.

Ideally, the particles are relatively soft. Generally, the particleshave an average hardness of less than 10 Mohs, typically less than 8Mohs, and preferably less than 6 Mohs. Typically, the particles willhave an average hardness of at least 1 Mohs, and preferably of at least2 Mohs. In a preferred embodiment of the invention, the particles willhave an average hardness of about 3 Mohs. Typically, the particles havean average maximum diameter of between 30 and 1000 microns.

The process of the invention may be a blasting operation or a manualrubbing operation.

When the process of the invention is a blasting operation, various meansof blasting are envisaged, such as for example, mechanical projection(i.e. centrifugal particle acceleration), pneumatic particle projectionand electrostatic particle projection. A mechanical particle projectingdevice which is suitable for carrying out the process of the inventionis described in published International Patent Application NoPCT/EP00/09960. Generally speaking, dry blasting is envisaged. However,in certain circumstances wet blasting may be appropriate whereby a wetcomponent of the treating agent is non-aqueous. Such a wet component maybe a non-aqueous solvent such as, for example, an alcohol.

When the process of the invention involves manual projection of theparticles along the surface, the particles may be rubbed along thesurface using a cloth, by hand, or by any other means such as, forexample, a mechanical polishing, brushing or rubbing apparatus or thelike.

The invention also relates to the use of the process of the invention indental applications such as teeth whitening, plaque removal and generalcleaning or polishing of the teeth, buccal cavity, and prosthetic partssuch as crowns, bridges and complete or partial dentures. As such, theprocess may involve either blast application using some form of particleaccelerator, or manual application, of the treating agent. Manualapplication includes conventional brushing, rubbing, polishing or thelike.

The invention also relates to the use of the process of the invention intreating bone.

The invention also relates to the use of the process of the invention incosmetic application. Thus, the process may be employed to remove skinin, for example, an exfoliating application.

The invention also relates to the use of the process of the invention intreating automobiles, bikes, aeroplanes, boats, casting dies, machinesand parts thereof. In addition, the process may be utilised in treatingand/or maintaining equipment in petrochemical, chemical and foodproduction facilities.

The invention also relates to an agent for treating a surface to cleanor otherwise treat the surface, the agent being of the type comprising aplurality of particles, the particles comprising a precipitate oragglomerate of an insoluble alkali metal salt, wherein the treatingagent is preferably substantially non-aqueous. Typically, the salt is acarbonate. Suitably the metal is calcium or magnesium.

The invention also relates to the use of a treating agent of theinvention in dental applications.

The invention also relates to the use of a treating agent of theinvention to treat bone.

The invention also relates to the use of a treating agent of theinvention in cosmetic applications, such as, for example, to removeskin.

The use of substantially non-aqueous treating agents has a number ofadvantages. Aqueous treating agents such as blasting slurries have atendency to freeze when used in countries where severe winters areencountered. Further, the presence of water in blasting slurries canhave the effect of contributing to erosion of the surface being cleaned.This problem is particularly acute when the surface being cleaned formspart of a structure or building. Moreover, the use of aqueous blastingslurries to treat surfaces having electrical components can beparticularly hazardous due to corrosion. Use of the process and treatingagents of the invention obviates these problems.

Use of the process of the invention has the effect of removing coatingswithout damaging the surface of the substrate. It should also bepossible to clean complete structures and equipment having complexgeometrical configurations such as valves, bridges, bearings,ballbearings etc having parts which are difficult to access withconventional cleaning equipment or conventional blasting jets.

After having cleaned or otherwise treated the substrate according to theprocess of the invention the treating agent is easily removed togetherwith the removed coating. The cleaning agent itself is environmentallyacceptable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription of some embodiments thereof, given by way of example only,with reference to the following figures in which:

FIG. 1 is an illustration of a particle of a treating agent according tothe invention; and

FIG. 2 illustrates the process of the invention.

DETAILED DESCRIPTION

The present invention has been found to be effective at removing varioustypes of coatings from substrates having hardness from that of steel towood (or even softer materials) without causing damage to the subtratessurface. The treating agent can easily be removed by flushing with wateror compressed air. The person carrying out the cleaning process is notexposed to any harm and the agent is acceptable from an environmentalpoint of view. The agent is also available in desired qualities,particle size, hardness etc.

Referring to the drawings, and initially to FIG. 1, there is illustrateda particle, indicated generally by the reference numeral 1, which isused in the process of the invention. The particle is a particle ofprecipitated calcium carbonate and has a generally round, and slightlyirregular, shape and a rough, irregular, surface configuration.

Referring to FIG. 2, the process of the invention is illustrated inwhich the particle 1 is projected towards a surface 2 having a coating 3to be removed. Due to the low angle of incidence of the particle 1 andthe surface 2, and the generally round shape of the particle 1, uponimpact the particle 1 rolls along the surface, rubbing the surface andabsorbing the coating 3 onto a surface of the particle. This has the neteffect of removing the coating from the surface without causing anydamage to the surface.

EXAMPLE 1

Method of production of particles.

Production of insoluble particles CaCO3 is carried out by providing freeCa⁺⁺ in a liquid with a PH over 7 by dissolving calcium oxide in water.

Addition of CO₂ results in the precipitation CaCO₃.Ca⁺⁺+2OH⁻+CO₂→CaCO₃+H₂O

Various other methods of production of particles forming part oftreating agents according to the invention have been investigated usingvarious types of substrates including plastic, metal and polymer.Examples of these methods include:

Chemical

There are numerous chemical methods for producing spherical powders.Generally, chemical methods result in very fine powder particle sizes.Such methods include Sol Gel, chemical precipitation, Reaction,reduction (hydrogen in an autoclave to reduce metal salts to the metal),decomposition (eg metal carbonyls) and Electrolysis.

Spray Drying

This is the most widely used industrial process involving particleformation and drying. It is highly suited for the continuous productionof dry solids in either powder, granulate or agglomerate form fromliquid feedstocks as solutions, emulsions and pumpable suspensions.

Agglomeration

The most common method of agglomeration is where the constituents arephysically mixed together with an organic binder. The solvent is thendriven off and the resultant material sized. The binder should be burntoff during spraying. This process is used in the manufacture of NiAl,AlSi or polyester powders. The most common method of agglomeration iswhere the constituents are physically mixed together with an organicbinder. The solvent is then driven off and the resultant material sized.The binder should be burnt off during spraying. This process is used inthe manufacture of NiAl, AlSi-polyester powders. The use of spray dryinghas become another common method for the agglomeration of powders. Here,a slurry is formed with the constituents and this is then fed into arotary spray head. Here, the slurry forms an atomised cloud which issolidified by an opposing warm air stream to produce a powder. Thismethod is used for ceramics such as zirconia and cermets such asWC-cobalt. The powder is largely spherical but in the as spray driedstate can be porous and friable. The material is often densified andstabilised by sintering and/or spray densification.

There are also methods of mechanical agglomeration (eg the Hosakawamethod) where for example a hard constituent is mechanically driven intoa softer matrix particle to form a composite powder. Indeed, simple ballgrinding can be used to mechanically alloy two or more constituentstogether. Although sintering can be used as part of the spray dryingprocess it can also be used alone as a method to manufacture powders.The constituents are mixed together and heated to get some solid statediffusion going and then the resultant product is crushed. A number ofrepeated cycles can be used to promote further alloying in which casethe powder is called a “reacted” powder.

Atomisation

There are a number of atomisation techniques which all rely on theproduction of a molten pool as the source. Atomisation methods includeRotating Electrode, Vibrating Electrode (arc), centrifugal (from a melt)and Rapid Solidification (eg aluminium ribbon). However, by far the mostcommonly used methods are either water or gas atomisation.

Others

-   -   Solid State Reduction    -   Electrolysis    -   Electrodeposition    -   Mechanical Comminution

As described above, the process of the invention may be carried outusing some form of particle accelerator, such as that described inInternational Patent Application No PCT/EP00/09960 and using theoperational parameters described in this Application, or by means ofmanual treatment of a surface.

The invention is not limited to the embodiments hereinbefore describedwhich may be varied in both construction and process step withoutdeparting from the invention.

1. A process for blasting a surface to remove a coating from thesurface, the process being of the type which employs an erasing agentcomprising a plurality of particles, the process comprising the step ofpropelling the erasing agent against the surface such that at least someof the particles roll along at least a portion of the surface, whereinan angle of incidence of the particles and the surface is between 0° and60°, wherein the particles are generally round and have an irregularsurface configuration to effect a rolling movement along the surfacesuch that the particles rub and absorb the coating from the surface, andwherein the particles have an average maximum diameter of between 30 and1000 microns, wherein each particle comprise a precipitate oragglomerate of an insoluble alkali metal carbonate.
 2. A process asclaimed in claim 1 for use with dental applications such as teethwhitening, plaque removal and general cleaning or polishing of theteeth, buccal cavity and prosthetic parts such as crowns, bridges andcomplete or partial dentures.
 3. A process as claimed in claim 1 inwhich the particles comprise a precipitate or agglomerate of aninsoluble calcium carbonate.
 4. A process as claimed in claim 1 in whichthe erasing agent is substantially non-aqueous.